I don't know much about Goroh, but it seems to me that another sword user would be too much. (Explains why Zelda seems to be sword-less, despite her having one in TP) I also have to wonder if Sakurai and Nintendo are aware of how popular Goroh seems to be? In any case, he's actually in the game, and maybe if he proves to be popular enough we'll see him get bigger roles in the future.
Anyways, as far as DK characters go, here's the way I see it. DK is a sure thing, because he's friggin' DK one of Nintendo's main mascots. As far as Diddy or K. Rool, I'd say they both still have a good shot at being playable.
The reason we didn't see ANY DKC characters other than DK for a long time was because in 2001/2002 Rare left Nintendo and became a Microsoft exclusive, laying off a ton of people in the process. There was a mini-battle over the DKC characters, because Rare still owned all of them except for DK himself.
They eventually got the characters back, and it shows since they were ALL featured in DK King of Swing, and both Diddy and Dixie have been making appearances in all the Mario sports titles. (And of course, Diddy was put in Double Dash as well)
And Diddy is much to popular to not be featured. I beleive he and Dedede were 2 of the top characters from when people could suggest their own characters on the old website. And as someone pointed out to me before in this thread, he does have alot of potential for a moveset.
Honestly, I think the Kremlings are more likely to be Assist Trophies than K. Rool. And if they want more villains, they've got one staring them right in the face with K. Rool.
As far as Dixie goes…...it depends on how many character slots they have if you ask me. I love Dixie and want her as playable, but if she ends up an assist trophy it'd make some sense and I could live with that.
Anyways, I know seeing Goroh as an assist trophy is a dissapointment for many, but to say that you're through with the whole game because of this is stupid. That guy didn't bring up any good points other than why Goroh had potential of being playable.